1. Water-soluble carbohydrates (mono, disaccharides). Functions of soluble carbohydrates:
a, b) Transportation of energy supply to the cell c) Have... are part of the mucus produced by the bronchi, which protects the lungs; are part of heparin - the anticoagulant system of the blood. d) Have... are part of the signaling complexes of membranes.
1.1. Monosaccharides: glucose - the main source of energy for cellular respiration; fructose - an integral part of the nectar of flowers and fruit juices; ribose and deoxyribose - structural elements of nucleotides, which are monomers of RNA and DNA.
1.2. Disaccharides: sucrose (glucose + fructose) - the main product of photosynthesis, transported in plants; lactose (glucose + galactose) - is a part of mammalian milk; maltose (glucose + glucose) - a source of energy in germinating seeds.
2. Insoluble carbohydrates (polymer): starch, glycogen, cellulose, chitin.
Functions of polymeric carbohydrates:
Glucose exists in the form of two isomers - α and β.
Starch consists of α-isomers, cellulose consists of β-isomers.
Starch - consists of branched spiralized molecules that form reserve nutrients in plant tissues.
Cellulose - a polymer formed by glucose residues consisting of several straight parallel chains connected by hydrogen bonds. This structure prevents water penetration and ensures the stability of the cellulose membranes of plant cells.
Chitin consists of amino derivatives of glucose. The main structural element of the integument of arthropods and the cell walls of fungi.
Glycogen - a reserve nutrient of an animal cell.
Lipids
Lipids - esters of fatty acids and glycerin. Insoluble in water, but soluble in non-polar solvents (acetone, gasoline). Present in all cells. Lipids are made up of hydrogen, oxygen and carbon atoms.
Lipid functions:
Structural - phospholipids are part of cell membranes.
Storing - fats are stored in the tissues of vertebrates.
Energy - the effect of the breakdown of 1 g of fat - 39 kJ, which is twice the energy effect of the breakdown of 1 g of glucose or protein. Fats are also used as a source of water, because when fat is broken down, water is released (camel).
Protective - the subcutaneous fat layer protects the body from mechanical damage (shock-absorbing properties).
Heat insulating - subcutaneous fat helps to retain heat, as it has a low thermal conductivity.
Electrical insulating - myelin secreted by Schwann cells, which form the sheaths of nerve fibers, isolates neurons, which greatly speeds up the transmission of nerve impulses.
Nutritious - many fat-like substances contribute to building muscle mass, maintaining the tone of the body.
Lubricating - waxes cover the skin, wool, feathers and protect them from water. The leaves of many plants are coated with a wax coating; wax is used in the construction of honeycombs.
Hormonal - adrenal hormone - cortisone and sex hormones are lipid in nature.
Biologically active substances - chemicals necessary to maintain the vital activity of living organisms, which have high physiological activity at low concentrations in relation to certain groups of living organisms or their cells, malignant tumors, selectively retarding (or accelerating) their growth or completely suppressing their development.
Natural biologically active substances are formed in the process of vital activity of living organisms. They can be formed in the process of metabolism, being released in environment (exogenous) or accumulate inside the body (endogenous). The efficiency of the synthesis of biologically active substances depends on the physiological characteristics of living organisms, environmental factors.
Exogenous natural biologically active substances include:
colins - organic compounds secreted by higher plants through the root system, causing the oppression of lower plants;
phytoncides - volatile organic compounds released by higher plants into the atmospheric air, causing the death of pathogenic microorganisms;
antibiotics - organic substances - metabolic products of microorganisms, released into the environment or accumulated inside the cell, suppressing or inhibiting other types of microorganisms;
marasmins - organic substances secreted by microorganisms, causing the oppression of lower plants.
The impact of some living organisms on others due to the production of biologically active substances is called allelopathy.
Mycotoxins are biologically active substances produced by fungi (of the genus Fusarium, Aspergillus, etc.) in the process of metabolism, which are released into the body of higher plants (cereals) during their joint development, and cause disease of the latter. The danger of mycotoxins is associated with their stability during storage, heat treatment, the ability to quickly spread in organs and tissues of the body, causing inhibition of protein synthesis, damage to the cardiovascular system, bone marrow cells, lymph nodes. Many mycotoxins are carcinogenic.
Endogenous biologically active substances include: proteins, fats, carbohydrates, amino acids, vitamins, enzymes, hormones, dyes.
Proteins are natural polymers whose molecules are built from amino acid residues. By their structure, proteins are divided into simple and complex. Proteins (from the Greek protas - the first, important) are simple proteins. These include albumins, globulins, glutemins.
Proteids are complex proteins that, in addition to protein macromolecules, contain non-protein molecules. These include nucleoproteins (contain nucleic acids in addition to protein), lipoproteins (contain lipids in addition to protein), phospholipids (contain phosphoric acid in addition to protein). Proteins play a key role in cell life. They are necessary for the formation of cells, body tissues, form the basis of biomembranes, as well as support the vital functions of living organisms. Proteins perform catalytic (enzymes), regulatory (hormones), transport (hemoglobin, myoglobin), structural (collagen, fibroin), motor (myosin), protective (immunoglobulin, interferon) functions that reduce the risk of infectious or stressful situations, as well as spare (casein, albumin), bioenergetic functions. In turn, the biological activity of proteins is closely related to the amino acid composition. Proteins contain 20 amino acids and two amides (aspartine, glutamine). Plants and most microorganisms are able to synthesize all of their constituent amino acids from simple substances - carbon dioxide, water and mineral salts. In the body of animals and humans, some amino acids cannot be synthesized and must be supplied ready-made as components of food. Such acids are called essential. These include: valine, leucine, isoleucine, lysine, methionine, threonine, tryptophan, phenylalanine. Long-term absence of at least one essential amino acid in the body leads to serious diseases of humans and animals. All essential amino acids must be contained in proteins in certain proportions that meet the needs of a given organism. If at least one amino acid is deficient, then other amino acids in excess are not used for protein synthesis. Proteins with an optimal amino acid content are considered biologically complete.
The amount of any amino acid missing to the norm is balanced by the addition of "pure" preparations of deficient amino acids or a protein mass having a higher content of this amino acid in comparison with the standard. In plants, the concentration of protein substances varies depending on growing conditions, climate, weather, soil type, agricultural technology and others. Many microorganisms are distinguished by a high intensity of protein synthesis, and the proteins of microbial cells have an increased content essential amino acids.
Vitamins are low molecular weight organic substances with high biological activity and acting as bioregulators. The biological activity of vitamins is determined by the fact that they, as active groups, are part of the catalytic centers of enzymes or are carriers of functional groups.
With a lack of these substances, the activity of the corresponding enzymes decreases and, as a result, the biochemical processes occurring with the participation of these enzymes are weakened or completely stopped, which leads to serious diseases. Human and animal organisms are not capable of synthesizing vitamins. Plants and microorganisms, which synthesize almost all vitamins (with the exception of B12), are the main source of their intake in humans and animals. Almost all vitamins contain a hydroxyl group (-OH) or a carbonyl group (-C \u003d O). Distinguish between fat-soluble and water-soluble vitamins.
Lipids are a complex mixture organic compounds with similar physical and chemical properties that are involved in the construction of cell membranes. They are an obligatory component of the cell. Their common feature is the presence of long-chain hydrocarbon radicals and ester groups in the molecule. By their chemical nature, fats are esters of glycerol and fatty acids, which differ in the nature of fatty acids.
In plants, fats accumulate in fruits and seeds, in animals and fish, they are concentrated in subcutaneous adipose tissues, abdominal cavity and tissues surrounding many important organs (heart, kidneys), as well as in brain and nerve tissues. Prolonged absence in a living organism leads to disruption of the central nervous system, decreases resistance to infections, and shortens life expectancy. To extract lipids, it is necessary to destroy their connection with proteins, carbohydrates and other components of the cell. When lipids are extracted from natural raw materials, a mixture is obtained, consisting of lipids and fat-soluble substances (pigments, vitamins, steroids).
Enzymes (Latin fermentum - sourdough), or enzymes (enzime - yeast) are protein biocatalysts that accelerate the metabolism in cells and have a molecular weight of 15,000 to 1,000,000.
Distinguish between single-component (monomeric) enzymes, consisting only of protein (folded polypeptide chains), and two-component, consisting of protein macromolecules and non-protein molecules. The enzyme activity is determined by the structure of the protein portion. Enzymes are used in various fields of human activity as biological catalysts. For a long time, mushrooms have been the main supplier of enzymes. Nowadays, bacterial enzymes are becoming more and more widely used. The accumulation of enzymes in cells can be increased 100-1000 times by genetic exchange and selection of nutrient media. Cultivation of enzyme producers is economical only when fermentation cycles are short, nutrient media are relatively cheap, and the specificity of intra- or extracellular enzyme proteins is high. Microbial enzymes are used as therapeutic agents in clinical analyzes, as well as as a feed additive (0.1-1.5% of dry mass of feed) to improve the efficiency of using plant feed (grain, silage, roughage, etc.) by farm animals containing indigestible substances: fiber, lignin, hemicellulose. So, for example, in ruminants, fiber is digested by 40-65%, vegetable proteins by 60-80%, lipids by 60-70%, starch and polyfructosides by 70-80%. In addition, enzyme preparations are used in the preparation of forage by ensiling to accelerate lactic acid fermentation.
Lipids are a large group of natural substances, diverse in chemical structure and physicochemical properties. There are several interpretations of the concept of lipids and various schemes for their classification based on the properties of these substances. The general property of lipid compounds is the ability to dissolve in ether, chloroform and other organic solvents (but not in water).
By structure, lipids can be divided into two large groups.
1. Simple lipids, or neutral fats, presented in most organisms by acylglycerols, ie, glycerol esters of fatty acids (free fatty acids are found in cells only as a minor component). 2. Complex lipids, which include lipids containing phosphoric acid in a mono- or diester bond, are phospholipids, which include glycerophospholipids and sphingolipids. Complex lipids include compounds bound by a glycosidic bond with one or more monosaccharide residues, or glycolipids, as well as compounds of steroidal and isoprenoid nature, including carotenoids.
Until the 1920s, lipids, especially neutral ones, were considered only as a reserve material that could be replaced with other substances of equal caloric value without much damage to the vital activity of the body. The first proof that lipids contain compounds physiologically necessary for higher animals was obtained in 1926 by the Dutch researchers Ivans and Boer. Somewhat later it was found that these compounds are polyunsaturated fatty acids (linoleic, linolenic and arachidonic) - physiologically necessary for most living organisms (vitamin F).
Later it was found that in the cells of microorganisms lipids perform a variety of biological functions. They are part of such critical structures as the cell membrane, mitochondria, chloroplasts, and other organelles. Lipoprotein complexes play an important role in metabolic processes. They are largely associated with the active transfer of various substances through the boundary membranes and the distribution of these substances within the cell. The composition of lipids is largely associated with such properties of organisms as thermotolerance and thermophilicity, psychrophilicity, acid resistance, virulence, resistance to ionizing radiation and other signs. In addition, lipids can function as storage products. These include poly-β-hydroxybutyric acid, formed by many bacteria, and acylglycerols, in particular tridcylglycerol, accumulated in large quantities by some yeasts and other fungi.
A systematic study of the lipids of microorganisms began in 1878 after the report of the German researchers Nägeli and Loew on the formation of fat droplets in yeast growing under conditions of abundant oxygen supply. The total amount of lipids in microorganisms usually ranges from 0.2 to 10% of the absolutely dry matter of the cell. However, under conditions favorable for the accumulation of these metabolic products, the lipid content can reach 60-70% of dry matter. Only some representatives of microorganisms have the ability to such "oversynthesis" of lipids. Of filamentous fungi, significant amounts of lipids (40 - 70%) are formed by representatives of the genera PeniclUium, Rhizopus, Fusarium and some others. Yeast synthesizes approximately the same amount of lipids - representatives of the genera Cryptococcus, Rhodotorula, Lipomyces, Sporobolomyces. Among bacteria, mycobacteria are interesting, they can accumulate up to 40% of lipids. In a number of bacteria, the amount of polyhydroxybutyrate reaches 60%, for example, in the hydrogen-oxidizing species Alcaligenes eutrophus. Under certain conditions of cultivation, up to 60% or more lipids accumulate some microforms of algae.
Maximum lipid content in some microorganisms
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Microorganism |
Lipids in relation to dry matter of cells,% |
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Actinnmyccs albaduncus |
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Alcatigenes eutrophus |
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Miiciibacterlum smegmatis |
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Ps ".iuintnonas mallei |
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Cryplncoccus terricolus |
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E "ncloniycopsis vernalis |
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Lipomyces Upoferus |
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Lipomyces starkeyl |
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Rhodoiorula gracilis |
|
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Sporobolomyces roseus |
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Blacesiea trispora |
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Geotrichum candidum |
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Geotrichum wallroth |
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PenicHHum yavanicutn |
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Rhizopus arrhizus |
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Chlorella pyrenoidosa |
The lipid composition of various microorganisms is often different. Bacteria usually have a lot of phospholipids. Mycobacteria contain significant amounts of waxes, while in archaea, neutral lipids are represented by simple isopropylglycerol esters, i.e. they do not contain fatty acids, the presence of which is characteristic of other organisms. Fatty acids in eubacteria usually contain from 10 to 20 carbon atoms (mainly 15-19). Among them are saturated acids with a straight chain of carbon atoms, monounsaturated with a straight chain, with a branched chain (iso- and ante-iso), with a cyclopropane ring and hydroxyacids. But the vast majority of bacteria lack the polyunsaturated fatty acids typical of lipids in eukaryotic organisms.
Fatty acids of mycobacteria and related forms are more complex than those of other bacteria. In addition to the usual fatty acids, mycobacteria, corynebacteria and nocardia contain in the composition of lipids peculiar mycolic acids characteristic only of these microorganisms, which are high molecular weight β-hydroxy acids with a long aliphatic chain in the b-position.
Fatty acids with a cyclopropane ring are widespread in gram-positive and gram-negative eubacteria (bacilli, clostridia, streptococci, enterobacteria, and brucella).
Actinomycetes and bacilli are characterized by a high content of branched fatty acids, the amount of which reaches 80% of the total fatty acids.
The fatty acid composition of the lipids of filamentous fungi is in many respects identical to the composition of vegetable oils. In this regard, mushroom lipids can be used in various industries. national economy (agriculture, paint and varnish industry, production of medicines). IN last years Among filamentous fungi, highly active producers of arachidonic acid have been found and a method has been developed for its transformation into certain prostaglandins (biologically active substances, which are derivatives of polyunsaturated fatty acids, the molecule of which contains 20 carbon atoms).
Of the yeast, the most studied is the composition of lipids in representatives of the genera Candida, Saccharomyces, Rhodotorula, Cryptococcus. Fatty acids from C4 to C26 were found in saccharomycetes. In aerobic and anaerobic Saccharomyces cultures, the composition of fatty acids is significantly different. Long-chain fatty acids (C22, C24, C26) are more common in the yeast of the genus Rhodotorula than in Lipotnyces and Cryptococcus. The composition of fatty acids in algal lipids is similar to that of various plants.
Along with intracellular, some types of yeast and filamentous fungi have the ability to form extracellular lipids. There are descriptions of several forms of lipids found in the environment. In Pullularia, Rhodotorula, and Hansenula cultures, extracellular lipids appear as droplets of various diameters. When the yeast Candida bogoriensis is grown by the deep method, extracellular lipids are found in the form of droplets of various diameters and in the form of long white crystals. Research chemical composition extracellular lipids have shown that four main types of these compounds are excreted by yeast:
1) polyol esters of fatty acids, in which saturated, unsaturated and hydroxy acids are linked by ester bonds with C5 and C6 polyols;
2) sphingolipids (tetraacetyl C18-phytosphingosine, etc.);
3) hydroxy acid sophorosides;
4) substituted acids, for example erythro-8, 9, 13-triaceto-xidocosanoic acid.
Triacylglycerols are not found in the composition of extracellular lipids. A comparative study of the extra- and intracellular lipids of Rhodotorula glutinis showed significant differences in their fatty acid composition. In intracellular lipids, only six organic acids were identified (the main one is oleic). In addition, C19, C20, hydroxystearic and hydroxyaraquinic saturated acids were absent in intracellular lipids. The latter two together account for more than 50% of all fatty acids in extracellular lipids.
An inverse relationship is observed between the synthesis of extracellular lipids and polysaccharides. At a cultivation temperature below the optimum in R. igtutinis, there is a sharp inhibition of the synthesis of extracellular lipids and significant amounts of exopolysaccharides accumulate in the medium. The same phenomenon is observed under low pH conditions.
Numerous experiments have shown that yeast lipids and products of their processing can be used in a wide variety of sectors of the national economy: in the textile, ceramic, leather, metalworking (rolled steel sheet, wire drawing, tin tinning) industries. Yeast lipids can also be used in the production of rubber, rubber, pharmaceuticals, cosmetics, soap, drying oils, in ore flotation processes, etc. Finally, as experiments have shown, yeast lipids can find great use in feeding farm animals and poultry. In this case, the process of their extraction from cells is excluded from the scheme of lipid production - the fat-rich biomass of microorganisms is used for feeding purposes.
After the Second World War, a significant amount of work was aimed at finding the possibility of obtaining microbial lipids for food purposes. The Swedish researcher Lundin showed that yeast fat (Rhodotocula gracilis), rich in physiologically essential fatty acids, can be successfully used in addition to technical and nutritional needs. A diet of 25 g of fatty yeast can provide the human body with 10 g of lipids, 6 g of protein and many other essential substances, which meets the daily requirement for these compounds by 20%.
The production of microbial fat for food purposes already took place in Germany during the First World War. Molasses or other sugar-containing substrates were used as a nutrient medium; the yeast-like fungus Endomycopsls vemails served as a producer. The food used was a biomass rich in fat, which was used to prepare a paste known as Evernal or Miceta.
By combining nutrient media, as well as by selecting the producer and the conditions for its cultivation, it is possible to obtain lipids that meet the composition of the requirements of various industries and agriculture... For example, when feeding birds, preference is given to lipids containing up to 65-70% unsaturated fatty acids. Microbial lipids containing a significant amount of fatty acids with two double bonds can be used for the preparation of varnishes and paints, as well as for the preparation of medicines that help prevent atherosclerosis and thrombosis. Lipids with a predominance of saturated fatty acids can be used for the production of technical lubricants. In the first cases, these requirements are met by the lipids of filamentous fungi and the yeast Lipomyces lipoferus, and in the second - the lipids of Candida humicola grown on wood hydrolyzate.
Summarizing what has been said, it should be noted that the composition of lipids (and hence the area of \u200b\u200btheir possible use) is largely due to the systematic position of the producer organism. At the same time, the ratio of individual components in the composition of lipids is determined by the specifics of the raw materials used and the physicochemical conditions of cultivation. These regularities of lipidogenesis are very important in organizing the industrial production of microbial fat, since under specific conditions they make it possible to obtain a product of a strictly defined composition and properties. Such controlled microbial synthesis can satisfy the requirements for lipids in various sectors of the national economy.
Technological role of carbohydrates Carbohydrates play an important role in the formation of food, biological and energy properties of food products. This is due to the fact that they themselves and their derivatives affect the taste, color, aroma, and stability of food products. Functions of mono- and oligosaccharides in food Hydrophilicity - due to the presence of numerous OH groups that interact with water through a hydrogen bond, as a result, this leads to the dissolution of sugars Related fragrances... Carbohydrates are essential for color and volatile flavor retention. This is important for products that use different types drying. To a greater extent, this property is expressed in disaccharides (in comparison with monosaccharides). Participate in education non-enzymatic browning products and aromatic substances. These reactions produce melanoidin pigments and various volatiles that affect food quality. Sweetness.The value of the sweetness of sucrose is taken as 100 units. Compared to sucrose, the sweetness of fructose is 180 units, glucose - 74 units, galactose - 32 units, lactose - 16 units. Functions of polysaccharides in food The functions of polysaccharides are related to their structural and functional properties, i.e. molecular architecture, size and the presence of intermolecular interactions, which are due to hydrogen bonds. Polysaccharides provide the formation of the structure and quality of food products - hardness, fragility, density, thickening, viscosity, stickiness, etc. It is thanks to polysaccharides that a sticky or fragile, swollen or jelly-like structure of food products is formed. The reaction of melanoidin formation is the 1st stage of non-enzymatic darkening reactions. An off-odor is often formed, which is undesirable. Therefore, you need to know the factors that influence this reaction in order to control it. These factors include: 1) Influence of pH of the medium... The most favorable acidity value is pH 7.8-9.2, darkening is less significant at pH \u003d 6. 2) Humidity... At very low or very high moisture content (a w \u003d 0; a w \u003d 1), darkening is not observed. Maximum darkening at intermediate moisture content. 3) Temperature... As the temperature rises, the reaction rate increases. An increase in temperature by 10 0 С gives an increase in speed by 2-3 times. four) Metal ions - intense darkening in the presence of copper or iron ions. five) Sugar structure - the way to form brown pigments decreases in the series: Pentoses: xylose arabinose Hexoses: galactose → mannose → glucose → fructose Disaccharides: maltose → lactose → sucrose 6) amino acid character: the further the amino group (–NH 2) is located from the carboxyl group, the more actively sugars participate in the Maillard reaction. If the reaction is undesirable, it can be inhibited by changing factors, or one of the components (usually sugar) can be removed. Thus, the important points of the melanoidin formation reaction: The formation of melanoidin pigments, desirable and undesirable, as well as the development of odor depends on the type of product. There may be a loss of essential amino acids, i. E. the biological value of the product is reduced. It has been suggested that some foods may be mutagenic, although it has not been definitively proven. Intermediates have antioxidant properties. This is due to the fact that intermediate decomposition products of fructoseamine, combining with peroxides or free radicals, slow down the oxidative process. This has a positive effect on the quality of the food during storage. There is evidence that the resulting foods impede the absorption of protein.7. From what residues of glucose (a- or b-form) are molecules built: a) starch, b) cellulose?
Fragment of amylopectin (starch) molecule
Fragment of a cellulose molecule
8. What chemical bonds in di- and polysaccharide molecules are called glycosidic bonds?
Lipids
Lipids are water-insoluble organic substances that can be removed from cells with organic solvents such as ether, chloroform and benzene. Classic lipids are esters of fatty acids and a trihydric alcohol of glycerol. They are called triacylglycerols or triglycerides.
The bond between carbonyl carbon and oxygen at the fatty acid alkyl group is called ester link:
Triacylglycerols are usually divided into fats and oils, depending on whether they remain solid at 20 ° C (fats) or have a liquid consistency (oils) at this temperature. The higher the proportion of unsaturated fatty acids, the lower the lipid's melting point.
Most of the fatty acids RCOOH contain an even number of carbon atoms, from 14 to 22 (most often R \u003d C15 and C17). In the composition of vegetable fats, unsaturated (having one or more double C \u003d C bonds) acids are usually found - oleic, linoleic and linolenic acids and saturated fatty acids, in which all C-C bonds are single. Some oils contain high levels of rare fatty acids. For example, castor oil obtained from castor bean seeds accumulates a lot of ricinoleic acid (see table).
Lipids contained in plants can be in the form of storage fat or be a structural component of the protoplast of cells. Storage and "structural" fats have different biochemical functions. Reserve fat is deposited in certain plant organs, most often in seeds, and is used as a nutrient during storage and germination. Protoplast lipids are essential part of cells and are contained in them in constant quantities. From lipids and compounds lipid nature (combinations with proteins - lipoproteins, carbohydrates - glycolipids) built a cytoplasmic membrane on the surface of cells and membranes of cellular structures - mitochondria, plastids, nuclei. Thanks to the membranes, the permeability of cells for various substances is regulated. The amount of membrane lipids in leaves, stems, fruits, roots of plants usually reaches 0.1-0.5% of the weight of wet tissue. The content of storage fat in the seeds of different plants is different and is characterized by the following values: in rye, barley, wheat - 2-3%, cotton, soybean - 20-30% (Fig. 4).
and - linen; b - sunflower; in - hemp; r - olive; d - soy
Interestingly, in about 90% of all plant species, not starch (like in cereals), but fats (like in sunflower) is deposited in seeds as the main storage substance. This is explained by the fact that storage fats are mainly used as a source of energy during seed germination. Deposition of fats in a reserve is beneficial for plants, since their oxidation releases about twice as much energy as oxidation of carbohydrates or proteins.
The main constants characterizing the properties of fat are its melting point, acid number, saponification number and iodine number. Below are the melting pointsome vegetable oils:
cottonseed oil -1 ... -6 ° C;
olive oil -2 ... -6 ° C;
sunflower oil -16 ... -18 ° C;
linseed oil -16 ... -27 ° C.
The acid number of fat is the number of milligrams of KOH alkali required to neutralize the free fatty acids contained in 1 g of fat. The acid number is used to control the quality of fats.
Saponification number - the number of milligrams of KOH alkali required to neutralize free acids and bound in the form of glycerides contained in 1 g of fat. The saponification number characterizes average molecular weight of fat.
Iodine number - the number of grams of halogen I 2, which can be added to 100 g of fat. The iodine number characterizes the degree of unsaturation of fatty acids in the fat. The iodine numbers of most vegetable fats are in the range of 100-160.
To be continued
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What are lipids?
Lipids are one of the groups of organic compounds of great importance for living organisms. According to their chemical structure, all lipids are divided into simple and complex. The molecule of simple lipids is composed of alcohol and bile acids, while complex lipids also contain other atoms or compounds. In general, lipids are of great importance to humans. These substances are found in a significant part of food products, are used in medicine and pharmacy, and play an important role in many industries. In a living organism, lipids in one form or another are part of all cells. From a nutritional point of view, it is a very important source of energy.
What is the difference between lipids and fats?
Basically, the term "lipids" comes from the Greek root meaning "fat", but these definitions still have some differences. Lipids are a broader group of substances, while fats are understood to mean only some types of lipids. Synonymous with "fats" are "triglycerides", which are obtained from the compound of alcohol glycerol and carboxylic acids... Both lipids in general and triglycerides in particular play a significant role in biological processes.Lipids in the human body
Lipids are found in almost all body tissues. Their molecules are in any living cell, and without these substances life is simply impossible. A lot of different lipids are found in the human body. Each kind or class of these compounds has its own functions. Many biological processes depend on the normal intake and formation of lipids. From the point of view of biochemistry, lipids are involved in the following important processes:
- energy production by the body;
- cell division;
- transmission of nerve impulses;
- the formation of blood components, hormones and other important substances;
- protection and fixation of some internal organs;
- cell division, respiration, etc.
The biological role of lipids in a living cell
Lipid molecules perform a huge number of functions not only on the scale of the whole organism, but also in each living cell separately. In fact, a cell is a structural unit of a living organism. It contains assimilation and synthesis ( education) certain substances. Some of these substances are used to maintain the vital activity of the cell itself, some - for cell division, and some - for the needs of other cells and tissues.In a living organism, lipids perform the following functions:
- energy;
- reserve;
- structural;
- transport;
- enzymatic;
- storing;
- signal;
- regulatory.
Energy function
The energetic function of lipids is reduced to their breakdown in the body, during which a large amount of energy is released. Living cells need this energy to maintain various processes ( respiration, growth, division, synthesis of new substances). Lipids enter the cell with blood flow and are deposited inside ( in the cytoplasm) in the form of small drops of fat. If necessary, these molecules are broken down, and the cell receives energy.Reserve ( storing) function
The reserve function is closely related to the energy function. In the form of fats inside cells, energy can be stored "in reserve" and released as needed. Special cells, adipocytes, are responsible for the accumulation of fat. Most of their volume is occupied by a large drop of fat. It is from adipocytes that adipose tissue in the body consists. The largest reserves of adipose tissue are found in the subcutaneous fat, the greater and lesser omentum ( in the abdominal cavity). With prolonged fasting, adipose tissue gradually breaks down, since lipid reserves are used to obtain energy.Also, adipose tissue deposited in the subcutaneous fat provides thermal insulation. Lipid-rich tissues are generally less conductive to heat. This allows the body to maintain a constant body temperature and not so quickly cool or overheat in different environmental conditions.
Structural and barrier functions ( membrane lipids)
Lipids play a huge role in the structure of living cells. In the human body, these substances form a special double layer that forms the cell wall. Thanks to this, a living cell can perform its functions and regulate metabolism with the external environment. The lipids that form the cell membrane also help maintain the shape of the cell.Why do lipids-monomers form a double layer ( bilayer)?
Monomers are chemicals ( in this case - molecules), which are capable of connecting to form more complex connections. The cell wall consists of a double layer ( bilayer) lipids. Each molecule that forms this wall has two parts - hydrophobic ( not in contact with water) and hydrophilic ( in contact with water). The double layer is obtained due to the fact that lipid molecules are deployed with hydrophilic parts inside the cell and outside. The hydrophobic parts are practically in contact, since they are located between two layers. Other molecules ( proteins, carbohydrates, complex molecular structures), which regulate the passage of substances through the cell wall.Transport function
The transport function of lipids is of secondary importance in the body. Only a few connections perform it. For example, lipoproteins, which are made up of lipids and proteins, carry substances in the blood from one organ to another. However, this function is rarely isolated, apart from considering it the main one for these substances.Enzymatic function
In principle, lipids are not part of the enzymes involved in the breakdown of other substances. However, without lipids, organ cells will not be able to synthesize enzymes, the end product of vital activity. In addition, some lipids play a significant role in the absorption of dietary fats. Bile contains a significant amount of phospholipids and cholesterol. They neutralize excess pancreatic enzymes and prevent them from damaging intestinal cells. Also, dissolution occurs in bile ( emulsification) exogenous lipids from food. Thus, lipids play a huge role in digestion and aid in the work of other enzymes, although they are not enzymes in themselves.Signal function
Some of the complex lipids have a signaling function in the body. It consists in maintaining various processes. For example, glycolipids in nerve cells are involved in the transmission of nerve impulses from one nerve cell to another. In addition, the signals within the cell itself are of great importance. She needs to "recognize" substances coming from the blood in order to transport them inside.Regulatory function
The regulatory function of lipids in the body is secondary. The lipids themselves in the blood have little effect on the course of various processes. However, they are part of other substances that are of great importance in the regulation of these processes. First of all, these are steroid hormones ( adrenal hormones and sex hormones). They play an important role in metabolism, growth and development of the body, reproductive function, and affect the functioning of the immune system. Also lipids are part of prostaglandins. These substances are produced during inflammatory processes and affect some of the processes in nervous system (e.g. perception of pain).Thus, lipids themselves do not perform a regulatory function, but their deficiency can affect many processes in the body.
Biochemistry of lipids and their relationship with other substances ( proteins, carbohydrates, ATP, nucleic acids, amino acids, steroids)
Lipid metabolism is closely related to the metabolism of other substances in the body. First of all, this connection can be traced in human nutrition. Any food consists of proteins, carbohydrates and lipids, which must enter the body in certain proportions. In this case, the person will receive both enough energy and enough structural elements. Otherwise ( for example, with a lack of lipids) proteins and carbohydrates will be broken down to generate energy.Also, lipids to one degree or another are associated with the metabolism of the following substances:
- Adenosine triphosphoric acid ( ATF). ATP is a kind of unit of energy inside the cell. When lipids are broken down, part of the energy goes into the production of ATP molecules, and these molecules take part in all intracellular processes ( transport of substances, cell division, neutralization of toxins, etc.).
- Nucleic acids. Nucleic acids are structural elements DNA and are found in the nuclei of living cells. The energy generated during the breakdown of fats is used, in part, for cell division. During division, new DNA strands are formed from nucleic acids.
- Amino acids. Amino acids are the structural components of proteins. In combination with lipids, they form complex complexes, lipoproteins, which are responsible for the transport of substances in the body.
- Steroids. Steroids are a type of hormone that contains significant amounts of lipids. With poor absorption of lipids from food, the patient may experience problems with the endocrine system.
Digestion and absorption of lipids ( metabolism, metabolism)
The digestion and absorption of lipids is the first step in the metabolism of these substances. The main part of lipids enters the body with food. In the oral cavity, food is chopped and mixed with saliva. Further, the lump enters the stomach, where chemical bonds are partially destroyed by the action of hydrochloric acid. Also, some chemical bonds in lipids are destroyed by the enzyme lipase contained in saliva.Lipids are insoluble in water, so in the duodenum they are not immediately digested by enzymes. First, the so-called emulsification of fats occurs. After that, the chemical bonds are cleaved by lipase coming from the pancreas. In principle, for each type of lipid, its own enzyme is now defined, which is responsible for the breakdown and assimilation of this substance. For example, phospholipase breaks down phospholipids, cholesterol esterase - cholesterol compounds, etc. All these enzymes are found in varying amounts in pancreatic juice.
The cleaved lipid fragments are absorbed separately by the cells of the small intestine. In general, the digestion of fats is a very complex process that is regulated by many hormones and hormone-like substances.
What is lipid emulsification?
Emulsification is the incomplete dissolution of fatty substances in water. In the food lump that enters the duodenum, fats are contained in the form of large drops. This prevents them from interacting with enzymes. In the process of emulsification, large fat droplets are "crushed" into smaller droplets. As a result, the area of \u200b\u200bcontact between the fat droplets and the surrounding water-soluble substances increases, and lipid breakdown becomes possible.The process of emulsifying lipids in the digestive system takes place in several stages:
- At the first stage, the liver produces bile, which will emulsify fats. It contains salts of cholesterol and phospholipids, which interact with lipids and promote their "crushing" into small droplets.
- Bile secreted from the liver accumulates in the gallbladder. Here she concentrates and stands out as needed.
- When fatty foods are consumed, a signal is sent to the smooth muscles of the gallbladder to contract. As a result, a portion of bile is secreted through the bile ducts into the duodenum.
- In the duodenum, the actual emulsification of fats and their interaction with pancreatic enzymes takes place. The contraction of the walls of the small intestine facilitates this process by "mixing" the contents.
Enzymes for the breakdown of lipids
For the digestion of each substance, the body has its own enzymes. Their job is to destroy chemical bonds between molecules ( or between atoms in molecules) so that nutrients can be normally absorbed by the body. Different enzymes are responsible for the breakdown of different lipids. Most of them are found in the juice secreted by the pancreas.The following groups of enzymes are responsible for the breakdown of lipids:
- lipase;
- phospholipases;
- cholesterol esterase, etc.
What vitamins and hormones are involved in lipid regulation?
Most lipids in human blood are relatively constant. It can fluctuate within certain limits. It depends on the biological processes occurring in the body itself, and on a number of external factors. The regulation of blood lipids is a complex biological process that involves many different organs and substances.The following substances play the greatest role in the assimilation and maintenance of a constant lipid level:
- Enzymes. A number of pancreatic enzymes are involved in the breakdown of lipids that enter the body with food. With a lack of these enzymes, the level of lipids in the blood may decrease, since these substances simply will not be absorbed in the intestines.
- Bile acids and their salts. Bile contains bile acids and a number of their compounds, which contribute to the emulsification of lipids. Normal lipid assimilation is also impossible without these substances.
- Vitamins. Vitamins have a complex strengthening effect on the body and directly or indirectly also affect lipid metabolism. For example, with a lack of vitamin A, the regeneration of cells in the mucous membranes worsens, and the digestion of substances in the intestine also slows down.
- Intracellular enzymes. The cells of the intestinal epithelium contain enzymes that, after absorption of fatty acids, convert them into transport forms and send them into the bloodstream.
- Hormones. A number of hormones affect metabolism in general. For instance, high level insulin can strongly affect blood lipid levels. That is why some norms have been revised for patients with diabetes mellitus. Thyroid hormones, glucocorticoid hormones, or norepinephrine can stimulate the breakdown of adipose tissue with the release of energy.
Biosynthesis ( education) and hydrolysis ( decay) lipids in the body ( anabolism and catabolism)
Metabolism is a set of metabolic processes in the body. All metabolic processes can be divided into catabolic and anabolic. The catabolic processes include the splitting and disintegration of substances. For lipids, this is characterized by their hydrolysis ( breakdown into more simple substances ) in the gastrointestinal tract. Anabolism combines biochemical reactions aimed at the formation of new, more complex substances.Lipid biosynthesis occurs in the following tissues and cells:
- Intestinal epithelial cells. Absorption of fatty acids, cholesterol and other lipids occurs in the intestinal wall. Immediately after this, new, transport forms of lipids are formed in the same cells, which enter the venous blood and are sent to the liver.
- Liver cells. In liver cells, some of the transport forms of lipids break down, and new substances are synthesized from them. For example, the formation of compounds of cholesterol and phospholipids occurs here, which are then excreted in the bile and contribute to normal digestion.
- Cells of other organs. Part of the lipids passes through the blood to other organs and tissues. Depending on the type of cells, lipids are converted into a certain type of compound. All cells, one way or another, synthesize lipids to form a cell wall ( lipid bilayer). In the adrenal glands and gonads, steroid hormones are synthesized from part of the lipids.
Resynthesis of lipids in the liver and other organs
Resynthesis is the process of formation of certain substances from simpler ones that were assimilated earlier. In the body, this process takes place in the internal environment of some cells. Resynthesis is necessary in order for tissues and organs to receive all the necessary types of lipids, and not just those that were consumed with food. Resynthesized lipids are called endogenous. The body spends energy on their formation.At the first stage, lipid resynthesis occurs in the intestinal walls. Here, the fatty acids supplied with food are converted into transport forms, which are sent with the blood to the liver and other organs. A part of the resynthesized lipids will be delivered to the tissues, from the other part, the substances necessary for vital activity are formed ( lipoproteins, bile, hormones, etc.), the excess is converted into adipose tissue and stored "in reserve".
Are lipids part of the brain?
Lipids are a very important constituent of nerve cells, not only in the brain, but throughout the entire nervous system. As you know, nerve cells control various processes in the body by transmitting nerve impulses. In this case, all nerve pathways are "isolated" from each other so that the impulse comes to certain cells and does not affect other nerve pathways. This "isolation" is possible due to the myelin sheath of nerve cells. Myelin, which prevents the chaotic propagation of impulses, is about 75% lipids. As in cell membranes, here they form a double layer ( bilayer), which is wrapped around the nerve cell several times.The myelin sheath in the nervous system contains the following lipids:
- phospholipids;
- cholesterol;
- galactolipids;
- glycolipids.
Lipid hormones
Lipids play an important structural role, including being present in the structure of many hormones. Hormones that contain fatty acids are called steroid hormones. In the body, they are produced by the gonads and adrenal glands. Some of them are also present in the cells of adipose tissue. Steroid hormones are involved in the regulation of many vital processes. Their imbalance can affect body weight, the ability to conceive a child, the development of any inflammatory processes, and the functioning of the immune system. The key to normal production of steroid hormones is a balanced intake of lipids.Lipids are found in the following vital hormones:
- corticosteroids ( cortisol, aldosterone, hydrocortisone, etc.);
- male sex hormones - androgens ( androstenedione, dihydrotestosterone, etc.);
- female sex hormones - estrogens ( estriol, estradiol, etc.).
The role of lipids in skin and hair
Lipids are of great importance for the health of the skin and its appendages ( hair and nails). The skin contains the so-called sebaceous glands, which secrete to the surface a certain amount of secretion rich in fats. This substance has many useful functions.Lipids are important for hair and skin for the following reasons:
- a significant part of the hair substance consists of complex lipids;
- skin cells change rapidly and lipids are important as an energy resource;
- secret ( secreted substance) the sebaceous glands moisturize the skin;
- thanks to fats, the firmness, elasticity and smoothness of the skin are maintained;
- a small amount of lipids on the surface of the hair gives it a healthy shine;
- the lipid layer on the skin surface protects it from the aggressive effects of external factors ( cold, sun rays, microbes on the surface of the skin, etc.).
Lipid classification
In biology and chemistry, there are quite a few different classifications of lipids. The main one is chemical classification, according to which lipids are divided depending on their structure. From this point of view, all lipids can be divided into simple ( consisting only of oxygen, hydrogen and carbon atoms) and complex ( including at least one atom of other elements). Each of these groups has corresponding subgroups. This classification is most convenient, since it reflects not only chemical structure substances, but also partially determines the chemical properties. Biology and medicine have their own additional classifications using other criteria.
Exogenous and endogenous lipids
All lipids in the human body can be divided into two large groups - exogenous and endogenous. The first group includes all substances that enter the body from the external environment. The largest amount of exogenous lipids enters the body with food, but there are other ways. For example, when using various cosmetics or drugs, the body can also receive some amount of lipids. Their action will be predominantly local.After entering the body, all exogenous lipids are broken down and absorbed by living cells. Here, from their structural components, other lipid compounds will be formed, which the body needs. These lipids, synthesized by their own cells, are called endogenous. They may have a completely different structure and function, but they consist of the same "structural components" that entered the body with exogenous lipids. That is why, with a lack of certain types of fats in food, various diseases can develop. Some of the components of complex lipids cannot be synthesized by the body on its own, which is reflected in the course of certain biological processes.
Fatty acid
Fatty acids is a class of organic compounds that are the structural part of lipids. Depending on what kind of fatty acids are part of the lipid, the properties of this substance may change. For example, triglycerides, the most important energy source for the human body, are derived from glycerol alcohol and several fatty acids.Naturally, fatty acids are found in a wide variety of substances, from petroleum to vegetable oils. They enter the human body mainly with food. Each acid is a structural component for specific cells, enzymes or compounds. Once absorbed, the body converts it and uses it in various biological processes.
The most important sources of fatty acids for humans are:
- animal fats;
- vegetable fats;
- tropical oils ( citrus,